Snow melt systems are installed in areas where unwanted snow and ice are eliminated by heating the surface to a temperature above freezing. These areas include sidewalks, stairways, driveways, runways, parking lots, wheelchair ramps, football fields, dog tracks, etc. Two methods are used to heat the surface. One (Electric) involves the installation of resistive wire under the surface and passing an electrical current through the wires causing the wire to heat and thereby heating the surface. The second (Hydronic) method which is more common, uses tubing placed beneath the surface with a heated liquid pumped through. This liquid is usually water with an antifreeze additive.
At present there are four levels of control used for the start and stop function and the temperature control of the fluid. The most basic form of control uses an on/off switch that is manually switched on before it begins to snow, and is manually turned off after the snow fall has ended and the area to be cleared, is free of ice and snow. The second and slightly more sophisticated control uses a wind-up timer. The operator does not have to remember to turn off the system, but still needs to turn it on before the snow fall, and may need to wind the timer a second or third time if the area still has a snow or ice accumulation at the end of the first time interval. The third level of control uses a moisture and temperature sensor located in the area of the snow melt surface, but not in contact with the surface. It waits for two conditions to be true, its moisture sensor has detected moisture and the outdoor temperature is below a predetermined setting, typically 38 degrees Fahrenheit. When both conditions are true, its output turns on to start the snowmelt system. When one of the conditions are no longer true, the output remains active for some predetermined amount of time. The fourth and most elaborate system uses a moisture and temperature sensor that is located directly in the snow melt area. The objective of this system is to directly experience moisture and temperature as the snow melt area does. This control system is the most expensive and is affected by the location of the sensor in the slab.